This invention relates generally to portable viewing devices configured to be worn on a user's head and, more particularly, to viewing devices that permit the user to achieve a selected one of multiple desired viewing effects, including for example magnification over a relatively distant viewing range, magnification over a relatively close viewing range, and wide screen viewing.
Portable viewing devices are sometimes used to provide a magnified image for a user viewing a distant object, such as a television or video screen. Typically, however, the optical elements of such a device provide a focused image over only a limited range of viewing distances. Such devices thus are generally incapable of being conveniently adapted to provide magnification of both a video screen of a computer terminal, viewed at a close distance, and the screen of a large projection television, viewed across a large room. Moreover, such devices generally provide only a single level of magnification
Portable anamorphic viewing devices are known for providing horizontal magnification only, to allow a user to view television broadcasts of horizontally compressed, wide-screen motion pictures with the proper image proportions restored. An example of such a device is disclosed in U.S. Pat. No. 5,124,840. Such devices also can be used to provide a viewer with a three-dimensional viewing effect based on a display of specialized, horizontally compressed two-dimensional images.
Portable viewing devices of the kind described briefly above generally have included a convergence control, to vary the angle of the optical paths of the image as observed by the user's left and right eyes. However, such convergence controls generally have operated by pivoting only a single lens assembly for one eye, or have required individual angular adjustment of the lens assemblies for both eyes. In cases where only one such lens assembly is angularly moved with respect to the other, the convergence of the assemblies only approximates the natural bilateral convergence of the user's eyes. In cases where both lens assemblies are adjusted individually, a user can have difficulty in adjusting the assemblies in equal but opposite directions to correspond to natural eye convergence. Moreover, individual adjustment of the lens assemblies to correct for convergence is considered time consuming and cumbersome to the user, and it can introduce objectionable distortion.
Known portable viewing devices thus have a major limitation of being configured to a single optical function, such as two-dimensional magnification or anamorphic magnification, but not both. Moreover, even in the case of two-dimensional magnification, known portable viewing devices are restricted to a limited single level of magnification and to a narrow range of viewing distances that can be accommodated by a focus adjustment. Prior devices have not allowed a user to select from varying levels of magnification or to adjust for wide variations in viewing distances, depending on particular circumstances. Moreover, known portable viewing devices have provided convergence correction through adjustment of a single lens assembly with respect to the other, thus only approximating normal eye convergence, or through individual adjustment of both lens assemblies, requiring the user to carry out such adjustment by trial and error.
Thus, a need exists for a portable device configured to be worn on a user's head that provides the user with a capability of selecting between different optical functions, e.g., two-dimensional magnification and disanamorphic magnification. Moreover, a need exists for such a device that permits the user to select different levels of magnification and that permits the viewer to utilize the device over a wide range of viewing distances, from close-up to infinity. Moreover, a need exists for such a device that allows the user to effect bilateral convergence correction without having to adjust the angle of each lens assembly individually. The present invention satisfies these needs.